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From: Dan Williams <dan.j.williams@intel.com>
To: Jason Gunthorpe <jgg@mellanox.com>
Cc: Jerome Glisse <jglisse@redhat.com>,
	Christoph Hellwig <hch@lst.de>, Ben Skeggs <bskeggs@redhat.com>,
	 Felix Kuehling <Felix.Kuehling@amd.com>,
	Ralph Campbell <rcampbell@nvidia.com>,
	 "linux-mm@kvack.org" <linux-mm@kvack.org>,
	 "nouveau@lists.freedesktop.org" <nouveau@lists.freedesktop.org>,
	 "dri-devel@lists.freedesktop.org"
	<dri-devel@lists.freedesktop.org>,
	 "amd-gfx@lists.freedesktop.org" <amd-gfx@lists.freedesktop.org>,
	 "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 04/15] mm: remove the pgmap field from struct hmm_vma_walk
Date: Fri, 16 Aug 2019 10:21:41 -0700	[thread overview]
Message-ID: <CAPcyv4jgHF05gdRoOFZORqeOBE9Z7PhagsSD+LVnjH2dc3mrFg@mail.gmail.com> (raw)
In-Reply-To: <20190816122414.GC5412@mellanox.com>

On Fri, Aug 16, 2019 at 5:24 AM Jason Gunthorpe <jgg@mellanox.com> wrote:
>
> On Thu, Aug 15, 2019 at 08:54:46PM -0700, Dan Williams wrote:
>
> > > However, this means we cannot do any processing of ZONE_DEVICE pages
> > > outside the driver lock, so eg, doing any DMA map that might rely on
> > > MEMORY_DEVICE_PCI_P2PDMA has to be done in the driver lock, which is
> > > a bit unfortunate.
> >
> > Wouldn't P2PDMA use page pins? Not needing to hold a lock over
> > ZONE_DEVICE page operations was one of the motivations for plumbing
> > get_dev_pagemap() with a percpu-ref.
>
> hmm_range_fault() doesn't use page pins at all, so if a ZONE_DEVICE
> page comes out of it then it needs to use another locking pattern.
>
> If I follow it all right:
>
> We can do a get_dev_pagemap inside the page_walk and touch the pgmap,
> or we can do the 'device mutex && retry' pattern and touch the pgmap
> in the driver, under that lock.
>
> However in all cases the current get_dev_pagemap()'s in the page walk
> are not necessary, and we can delete them.

Yes, as long as 'struct page' instances resulting from that lookup are
not passed outside of that lock.


  reply	other threads:[~2019-08-16 17:21 UTC|newest]

Thread overview: 56+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-06 16:05 hmm cleanups, v2 Christoph Hellwig
2019-08-06 16:05 ` [PATCH 01/15] amdgpu: remove -EAGAIN handling for hmm_range_fault Christoph Hellwig
2019-08-06 16:05 ` [PATCH 02/15] amdgpu: don't initialize range->list in amdgpu_hmm_init_range Christoph Hellwig
2019-08-06 16:05 ` [PATCH 03/15] nouveau: pass struct nouveau_svmm to nouveau_range_fault Christoph Hellwig
2019-08-06 18:02   ` Jason Gunthorpe
2019-08-06 16:05 ` [PATCH 04/15] mm: remove the pgmap field from struct hmm_vma_walk Christoph Hellwig
2019-08-07 17:45   ` Jason Gunthorpe
2019-08-07 18:47     ` Dan Williams
2019-08-08  6:59       ` Christoph Hellwig
2019-08-14  1:36         ` Dan Williams
2019-08-14  7:38           ` Christoph Hellwig
2019-08-14 13:27             ` Jason Gunthorpe
2019-08-14 14:48               ` Dan Williams
2019-08-15 18:03                 ` Jerome Glisse
2019-08-15 19:22                   ` Jason Gunthorpe
2019-08-15 19:36                   ` Dan Williams
2019-08-15 19:43                     ` Jerome Glisse
2019-08-15 20:12                       ` Dan Williams
2019-08-15 20:33                         ` Jerome Glisse
2019-08-15 20:41                           ` Jason Gunthorpe
2019-08-15 20:47                             ` Dan Williams
2019-08-16  0:40                               ` Jason Gunthorpe
2019-08-16  3:54                                 ` Dan Williams
2019-08-16 12:24                                   ` Jason Gunthorpe
2019-08-16 17:21                                     ` Dan Williams [this message]
2019-08-16 17:28                                       ` Jason Gunthorpe
2019-08-16 21:10                                         ` Ralph Campbell
2019-08-15 20:51                             ` Jerome Glisse
2019-08-16  0:43                               ` Jason Gunthorpe
2019-08-16  4:44                                 ` Christoph Hellwig
2019-08-16 12:30                                   ` Jason Gunthorpe
2019-08-16 12:34                                     ` Christoph Hellwig
2019-08-16  4:41                           ` Christoph Hellwig
2019-08-06 16:05 ` [PATCH 05/15] mm: remove the unused vma argument to hmm_range_dma_unmap Christoph Hellwig
2019-08-06 16:05 ` [PATCH 06/15] mm: remove superflous arguments from hmm_range_register Christoph Hellwig
2019-08-06 16:05 ` [PATCH 07/15] mm: remove the page_shift member from struct hmm_range Christoph Hellwig
2019-08-07 17:51   ` Jason Gunthorpe
2019-08-06 16:05 ` [PATCH 08/15] mm: remove the mask variable in hmm_vma_walk_hugetlb_entry Christoph Hellwig
2019-08-06 18:02   ` Jason Gunthorpe
2019-08-06 16:05 ` [PATCH 09/15] mm: don't abuse pte_index() in hmm_vma_handle_pmd Christoph Hellwig
2019-08-07 17:18   ` Jason Gunthorpe
2019-08-06 16:05 ` [PATCH 10/15] mm: only define hmm_vma_walk_pud if needed Christoph Hellwig
2019-08-06 16:05 ` [PATCH 11/15] mm: cleanup the hmm_vma_handle_pmd stub Christoph Hellwig
2019-08-06 18:00   ` Jason Gunthorpe
2019-08-06 16:05 ` [PATCH 12/15] mm: cleanup the hmm_vma_walk_hugetlb_entry stub Christoph Hellwig
2019-08-06 16:05 ` [PATCH 13/15] mm: allow HMM_MIRROR on all architectures with MMU Christoph Hellwig
2019-08-06 16:05 ` [PATCH 14/15] mm: make HMM_MIRROR an implicit option Christoph Hellwig
2019-08-06 17:44   ` Jason Gunthorpe
2019-08-06 16:05 ` [PATCH 15/15] amdgpu: remove CONFIG_DRM_AMDGPU_USERPTR Christoph Hellwig
2019-08-06 17:44   ` Jason Gunthorpe
2019-08-06 17:51     ` Kuehling, Felix
2019-08-06 18:58       ` Alex Deucher
2019-08-06 20:03         ` Jason Gunthorpe
2019-08-07  6:57           ` Koenig, Christian
2019-08-07 11:46             ` Jason Gunthorpe
2019-08-07 18:17 ` hmm cleanups, v2 Jason Gunthorpe

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